1. Field of the Invention
This invention relates to an addition curing type silicone rubber composition containing a platinum series catalyst, and more particularly, to a silicone rubber composition which is stabilized against premature gelation at room temperature.
2. Prior Art
Conventional silicone rubber compositions are loaded with platinum series catalysts for promoting addition reaction between an aliphatic unsaturated group-containing organopolysiloxane and an organohydrogenpolysiloxane. The crosslinking rate of this addition reaction is generally high albeit some dependency on the activity of the catalysts. As a consequence, control agents or curing inhibitors are added to most compositions for preventing premature gelation at room temperature, thereby imparting potential curability to the compositions in the sense that the composition are stable and remain unchanged over a long period of time, but can be cured by heating.
Known such control agents are ethylenically unsaturated isocyanurates and compounds having a hydroperoxide --C--O--O--H structure as disclosed in Japanese Patent Publication (Jp-B) Nos. 41626/1980 and 20340/1982. However, the former control agents are less effective for controlling the platinum series catalysts. The latter control agents must be added in a carefully controlled amount because otherwise vulcanization does not take place or the vulcanization rate is slow.
For preventing premature gelation at room temperature, it is also proposed to contain the platinum series catalyst and the organohydrogenpolysiloxane in separate packs which are mixed on use. This requires an additional operation of mixing two components.
Although a number of premature gelation inhibitors are currently available, many control agents, typically acetylene alcohol agents are volatile. Since they lose control ability by volatilization, they cannot survive over a long working life. Such control agents must be added in excess of the necessity.